Stabilized organic compositions



. oxidation of the lubricant.

retested Apr. 27, 1948 STABILIZED ORGANIC COMPOSITIONS m... J. Yates,Martinez, cum, asslgnor a Shell Development Company, San Francisco, cum.a corporation of Delaware No Drawing- Aliplication November 4, 1944,

Serial N0. 562,039

'lClalms. (Cl-252-51-5) This invention relates to compounded lubricatingoil and to organic compositions possessing unusual oxidation stabilityand other desirable qualities due to the presence of theherein-described additives. I

- Organic compositions undergo oxidation upon exposure to air. Thisprocess is accentuated by increased temperature such as occurs inengines and other operating machinery. When such organic compositionsare used as machinery lubricants, their stability is still furtherdrastically reduced due to their contact with metal surfaces which giveup metal into the lubricant. Such dissolved metals or metal salts act asoxidation catalysts in the lubricant and their action seems to beparticularly drastic when both iron and copper are present. In addition,water also causes corrosion of metal parts and accentuates Such water,even though not originally present in the oil, may come from a varietyof sources such as condensa- Further, application of the presentadditionagents is not limited to their use in hydrocarbon or mineral oil(petroleum) compositions but they may be employed similarly inlubricants composed in whole-or in part of animal or vegetableingredients such as natural waxes, sperm oil,

whale oil, palm oil. Jojoba oil, olive oil, Perilla oil, linseed oil,tung oil, soyabean oil, .iiaxseed oil,

tallow, lard, stearine pitch, etc.. as well as socalled syntheticlubricants such as polymerized olefins, alcohols", esters, etc.

Likewise, employment of the present additives is not limited to theiruse in lubricating composition from the atmosphere due to changes intemtions but they are broadly applicable to the stabilization of anyorganic compositions which are likely to come in contact with metalwhether at elevated temperatures or not. They may be used lem twoadditives-that is, an anticorrosive agentand an antioxidants-rather thantry to make one additive perform both functions. A primary reason forthis is that different amounts of the two types of ingredients areusually required.

to high temperatures in the presence of iron, copper and water. Theoccurrence of rusting also contributes to the degradation of the oil andthe rust may circulate through the oil system,interfere with clearancesand clog delicate engine parts such as the governor mechanism. Inaddition, specifications for turbine lubricants require that the mineraloil base be highly refined and this. although it improves the lubricantin other respects, unfortunately tends to remove natural oxidationinhibitors from the oil. Further, since the prevention or minimizationof emulsions is also an essential requirement in turbine operations, theuse of many otherwise beneficial additives is precluded because of theirtendency to contribute to emulsion formation.

Turbine oils can be produced, for example. from well refined lubricatingoils of the proper viscosity range which may be about 75 to 750 Say.Univ. sec. at 100 F. V

Similar problems of oxidation stability of lubricants used in contactwith metal surfaces arise in connection with damping or hydraulic oils,tranformer or electrical insulating oils. reirlgerator oils, etc.

Also, since the anticorrosive agent generally functions by forming afilm on the metal surface,- if it were also employed as an antioxidantthis film formation would withdraw it from the solution, thusdiminishing the oxidation protection 1 of the organic composition.

The corrosion or rust inhibitor used'inthe; present combination is arelatively high molecu-v lar weight dibasic acid. By dibasic acid ismeant anacid having two acidic or ionizablehydrogen ions. The two acidicradicals should be separated by no more than about four carbon atoms andpreferably by no more than two or three. Such acids are, for instance,high molecular weight saturated or unsaturated polycarboxylic acidsstable under ordinary lubricating conditions, such as alkylatedaliphatic polycarboxylic acids like alkylated succinic, glutaric,adipic, etc., acids. The oxygen in the acid radicals may also be replaced in whole or in part by sulfur to give the corresponding thioequivalents as thiolic (COSH), thionic -CBOH), or thionothiolic (-CSSH)acids.

The may also be monocarboxylic acids whose second acidic hydrogen atomis supplied or activated by a radical such as hydroxyl. nitro, nltroso,cyano, hydrosulflde, or aromatic sulionyl which is not more than abouttwo or three carbon atoms monocarboxylic acids themselves should containa minimum of 12 to 16 carboh atoms in addition to the added radical.Thus, taking stearic acid as an example, its dibasiccorrosion-inhibiting derivatives would be alpha or, beta hydroxystearicacid, alpha or beta nitrostearic acid, alpha or beta nitrosostearicacid, alpha or beta cyanostearic acid, alpha or beta mercaptostearicacid, alpha or beta phenylsulfonylstearic acid, etc,

One. or both of the acidic groups may be attached to an aromaticnucleus, as in alkylated salicylic acid (e. g. .di-isopropylsalicylicacid), alpha (orthocarboxyl aryloxy) carboxylic acids. e. g.

ocncoon uHu nooo

etc.

One may also use dibaslc acids wherein the two 'acidic groups are joinedthrough an oxygen, sulfide, disulfide or nitrogen linkage, as

RCH(CHa)-COOH (a-c-coon on are also effective dibaslc corrosioninhibitors.

These corrosion inhibitors may also contain ether, amino. sulfide,disulflde, etc., radicals elsewhere in the molecule. Those dibasic acidshaving at least one carboxylic radical are preferred. Mixtures of-thevarious dibasic acids. as well as the pure compounds, may be used.

The saturated acids are preferred because of their greater stabilitytoward oxidation which results in longer active life. Also,thesecorrosion inhibitors consisting only of carbon, hydrogen and oxygenare preferred. The most useful and practical dibasic acids for thepresent purposes are alkylated succlnic acids having a minimum of about16 carbon atoms and preferably those having 20 or more carbon atoms.Suitable acids may be produced by taking oleflns boiling above about 800C., such as may be obtained by cracking paraflin wax or by dehydrationof long chain fatty alcohols, etc., and condensing then with maleic acidanhydride to produce an alkylene succinic anhydride, hydrolyzing toproduce the corresponding free acid which may then be hydrogenated ifdesired. Such acids have been described in U. S. Patent No. 2,133,734.

The second additive in the present combination is an oil-soluble organiccompound in which have the basic formula wherein X represents no morethan two carbon,

nitrogen, oxygen, phosphorus, aluminum, boron, arsenic, antimony orsulfur atoms. Th9 WP! pounds in which X is a carbon or sulfur atom or adisulilde group are preferred.

The amine groups may be primary, secondary or tertiary. Thus, the aminonitrogen atoms, as well as the phenyl nucleii may carry such lowmolecular weight alkyl radicals as methyl, ethyl, normal and isopropyl,n-, iso-, secondary-, and tertiary-butyl, amyl, hexyl, heptyl, octyi andhigher homolcgs and isomers. When the valences of X are not all taken bythe two phenyl groups, the additional bonds may be occupied by likealkyl radicals, by hydrogen atoms, additional phenyl or aryl radicals,etc. Also, the phenyl radicals may, if desired, carry more than oneamino group. Thus, when X is a carbon atom, illustrative examples aretetramethyl diamino diphenyl methane, tetraethyl diamino diphenylmethane, tetramethyl triamino diphenyl methane, tetramethyl diaminotriphenyl methane, tetraethyl diamino triphenyl methane, and the like.The alkyl, aryl, aralkyl, alkaryl, alicyclic or heterocyclic radicalafllxed to X, to the amino groups or to the phenyl nucleii may also havesuch substituents as halogen or sulfur, and like radicals andsubstituents may also occur on the phenyl nucleus.

.The described antioxidants in which X is monoor di-sulfide may beillustrated by NW C. in the presence of water, oxygen and an iron coppercatalyst, the time required to build up a neutralization number of 2.0mg. KOH/gm. oil being determined. The essential features of the test areas follows:

The oxidation cell is a glass tube mm. x 600 mm. fitted with a mushroomwater condenser and an oxygen delivery tube with fritted glass outlet.The catalyst consists of lengths of No. 14 A. w. g. open-hearth ironwire and electro lytic copper wire, each three meters long and woundinto coils about 0.625 in. in diameter. The cell containing 300 ml. 011sample and the iron-copper catalyst is assembled with the condenser andoxygen' inlet tube and placed in a thermostatically controlled bathcapable of maintaining a temperature of i0.5 C. in the sample. Oxygen isadmitted at a rate of 3:0.5 liter per hour and at the end of 30 minutes,60 ml. of distilled water-is added to the cell. The test isthen-continued until acids areformed to the extent that theneutralization number of the oil reaches a value of 2.0.

In this test a turbine oil, refined from California petroleum, had anoxidation life of approximately hours by itself, Another sample of thesame 011, to which had been added 0.01% w. of saturated alkyl succinlcacid of approximately 370 molecular weight showed the same oxidationstability as the straight oil. A third sample of this turbine oil, towhich had been added 0.2% w. of tetramethyl diamino diphenyl methane hadan oxidation life of 2500 hours. A fourth sample, however, whichcontained both 0.01% of the alkyl succinic acid-and 0.2% of thetetramethyl diamino diphenyl methane exhibited an oxidation stability ofaround 6000 hours.

It will be noted that the corrosion inhibitor,

alkyl succinic acid, are not by itself appreciably ailect the oxidationstability of the oil (although it inhibited rusting oi the contingentmetal suriace) but, when the tetramethyl diamino diphenyl methane waspresent in addition, the oxidation life of the oil was more than doublethe expected additive effect which might be calculated from the resultwith each additive alone.

when the two are used together an adequate amount of both generally doesnot exceed a total oi 0.25 to 1%. The corrosion-inhibiting dibaslc acidshould be present-in a minimum of about 0.002595, the polyaminopolyphenyl compound in a minimum oi about 0.01%. Usually a combinedweight of 0.01 to 0.2% is satisfactory. although the combination oiadditives is not without eiiect even at much lower concentrations in aturbine or electrical insulating oil.

In some instances it may also be advantageous to incorporate anadditional antioxidant in about the same proportions as the polyaminopolyphenyl compound. The function of this supplemental antioxidant orthird additive is to reinforce the primary antioxidant. different typesof antioxidants seem to exhibit a maximum effectiveness in the presenceof particular metal surfaces or metallic oxidation catalysts and aminimum effectiveness with other metals. Hence when several diiierentmetals are in contact with the lubricant, it is well to haveantioxidants which are particularly effective toward two or more typesof metals. 1

Two classes oi supplemental antioxidants have been iound especiallyadvantageous in association with the present dibasic acid corrosioninhibitors and the polyamino polyph'enyl antioxidants. The first classconsists of the N-aryl naphthylamines, typified by phenyl alphanaphthylamine, phenyl beta naphthylamine and dinaphthylamines.

The second class consists of polyalkyl arylhydr'oxy compounds. That is,they may have only one hydroxyl group (alkyl phenols) or more than onehydroxyl group (alkyl cresol, alkyl resorcinol, etc.). Preferably shortalkyl groups-having up to about eight or ten carbon atoms-are attachedto the aromatic nucleus at the two, four and/or six positions;advantageously at least one of the alkyl radicals is a tertiary alkyl.Particular examples are ditertiary-butyl para-cresol,2,4-dimethyl-B-tertiary octylph'enol, pentamethylor pentaethyl-phenoland tritertiar-y-butyl phenol.

Sulfur-containing antioxidants may also be present. These should .have aminimum of about carbon atoms. Such antioxidant sulfur may This isdesirable because 6 Many suliur compounds naturally occurring inpetroleum oils are useiul antioxidants, pro video they have the properreactivity. This may be determined by heating such compounds with finelydivided metallic copper at 300' O. for 10 hours. These compounds inwhich about 20% to 60% oi the total suliur content reacts with the alsogood antioxidants..

Among the suliurized olefins found to beespeciaily useiul are, forexample: suliurized paramn wax (as produced by chlorination oi paramnwax. having a molecular weight between about 225 and 425.dehydrochlorination oi the chlorinated product to produce wax oleiins,and suliurization oi the latter): suliurized olefin or diolefin polymersboiling above about 400 C. such as obtained as lay-products in therefining of cracked distillates with clay or other refining agents, orin the polymerization oi normally gaseous olefins to produce gasoline orthe like (e. g. suliurized methyl pentadiene polymer); suliurized estersof unsaturated fatty acids with monohydric alcohols, as methyl, ethyl,propyl, etc. oleate, or linoleate; suliurized sperm oil; suliurizedjojoba oil; etc.

Also particularly efiective are the oil-soluble reaction products ofpolychlor parafi'in wax with sodium polysulfide which are compounds ofthe ype (Basin) J is 1'1 wherein n=2 or more.

A compounded lubricating oil may also contain other additiveslikeadditional corrosion inhibitors, such as sulfonic or iatty acids andtheir I bases include various nitrogen bases as primary,

be in the form of mercaptans, as in decyl mercaptans, dodecylmercaptans, cetyl mercaptans, oleyl mercaptans, stearyl mercaptans;butyl or other higher alkyl thiophenes: thionaphthols, alkylthionaphthols, etc.: or of polysulfides sulfide, etc.) 'or of sulfurcompounds formed by attaching sulfur to an oleflnic double bond (as a byreacting sulfur with olefinsat temperatures of about C. to 300 C.) whichcompounds are believed to contain the structure (sulfur in epithiollnkage) secondary, tertiary and quaternary amines.

Examples oi detergent forming acids are the various fatty acids oi, say,10 to 30 carbon atoms. wool fat acids, paraflln wax acids (produced byoxidation of parafiin wax), chlorinated fatty acids. aromatic carboxylicacids includingfaryl fatty acids, aryl hydroxy iatty 'acids, parafilnwax benzoic acids, various alkyl salicylic acids,

,phthalic acid mono esters, aromatic keto acids.

aromatic ether acids; diphenols as diialkyl phenol) sulfides anddisulfides, methylene bisalkyl-phenols; sulfonic acids such as may beproduced by treatment of alkyl aromatic hydrocarbone or high boilingpetroleum oils with sulfuric acid; sulfuric acid mono esters; phosphoricacid mono and di-esters, including the corresponding thiophosphoricacids, phosphonic and arsonic acids, etc.

Non-metallic detergents include compoundssuch as the phosphatides (e. g.lecithin) certain iatty oils as rapeseed oils, voltollzed iatty ormineral oils.

Other detergents are the alkaline earth phosphate di-esters, includingthe thiophosphate diesters; the alkaline earth diphenolates, speciiicalely the calcium and barium salts oij'diphenol as HCHC), CHiCHO, etc.)with alkylated aryl hydroxy products (such as alkyl phenol, alkylnaphthol, etc). They may be typified by the calcium salt oi the reactionproduct of iormalde- I hyde and iso-octyl phenol wherein n is a smallinteger such as 2, 3 or 4 or the product is a mixture of such polymers.

Detergents are employed in proportions of about A to about 5% weight.

The invention claimed is:

1. A refined mineral oil which is normally subject to oxidativedecomposition in the presence of a metal surface and containing a totalof about 0.01% to 0.5% by weight oi tetramethyldiamino diphenylmethaneand a saturated alkyl succinic acid of at least 16 carbon atoms, thetetramethyldiamino diphenylmethane being present in a minimum amount oiabout 0.01% and the balance, not less than 0.0025% beings, saturatedalkyl succinic acid, the total amount not exceeding 0.5% by weight. w

2. A mineral oil composition comprising a major proportion of a refinedmineral oil which is normally subject to oxidative decomposition in thepresence of a metal surface, a minimum amount of about 0.0025% of asaturated alkvl succinic acid of at least 16 carbon atoms and a I amountof the two additives not exceeding about 1.0% by weight.

3. A mineral oil composition comprising a major proportion of a mineraloil which is normally subject to oxidative decomposition in the presenceof a metal surface, a minimum amount of about 0.0025% of an alkylatedsuccinic acid of at least 16 carbon atoms and a minimum amount oi about0.01% of an N-alkylated diamino diphenylmethane, the total amount oi thetwo additivesnot exceeding about 1.0% by weight.

4. An organic composition comprising a major proportion of a mineral oilwhich is normally subject to oxidative decomposition in the presence oia metal surface, a minimum amount of about 0.0025% of an alkylatedsuccinic acid 01 at least 16 carbon atoms, and a minimum amount oi enceoi a metal suriacaa minimum amount-oi about 0.0025% 01 a-saturated alkylsuccinic-acid oi at least 16 carbon atoms, and a minimum amount oi about0.01% oi tetramethyldiamino diphenylmethane, the total amount oi the twoadditives not exceeding .about 1.0% byweight and a minor amount of about1.0% alkylarylhydroxy compound.

6. An organic composition comprising a major proportion of a mineral oilwhich is normally subjected to oxidative decomposition in the presenceoi a metal suriace, a minimum amount of about 0.0025% of a saturatedalkylsuccinic acid of at least 16 carbon atoms, and a minimum amount ofabout 0.01% of tetramethyldiamino oi a polydiphenylmethane. the totalamount oi the two additives not exceeding about 1.0% by' weight and aminor amount ,of about 1.0% of a phenyl alpha naphthylamine.

7. An organic composition comprising a major proportion of a mineral oilwhich is normally subjected to oxidative decomposition in the presenceof a metal surface, a minimum amount of about 0.0025% 01' a saturatedalkyl succinic acid oi at least 16 carbon atoms and a minimum amount oiabout 0.01% oi tetramethyldiaminodiphenylmethane, the total amount oithe two additives not exceeding about 1.0% by weight and a minor amountoi about 1.0% of a ditertiary-butyl-paracresol.

' WALLACE J. YATES.

7 REFERENCES CITED The following references are of record in the file oithis'patent:

Brandes .1..... June 4, 1940 about 0.01% oi tetrame'thyldiaminodiphenyl- ,methang the total amount oi the two'additives not exceedingabout "by weight and a minor ,amount oi about 1.0% oi an N-arylnaphthyl- "amine,

p 5. An organic composition comprising a major proportion oi a mineraloil which is normally. subjected to oxidative decomposition in the pres-Certificate of Correction Patent No. 2,440,530. April 27, 1948.

WALLACE J. YATES It is hereby certified that error appears in theprinted specification of the above numbered patent requiring correctionas follows:

Column 3, lines 70 to 72 inclusive, for the formula and that the saidLetters Patent should be read with this correction therein that the samemay conform to the record of the case in the Patent Oflice.

Signed and sealed this 8th day of March, A. D. 1949.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

